292 Mr. F. 8. Conant on Two new Chetognaths. 
Notes on the Classification of Chetognaths. 
Three systems have been advocated by the writers, and as 
none of them seems satisfactory when tested by Spadella 
schizoptera, it may be appropriate to review them briefly. 
Langerhans (Zeitschr. fiir wissench. Zool. Bd. xxxiv. 
pp. 182-136, 1880) forms three genera, based on fins and 
teeth :—Sagitta, with five fins (a caudal and two pairs of 
lateral) and two series of teeth; Krohnia, with three fins 
(caudal and one pair of lateral) and one series of teeth; and 
Spadella, with three—the caudal and lateral, however, being 
connected and lying wholly on. the tail-segment—and two 
series of teeth. Strodtmann (Archiv fiir Naturgesch. Year 58, 
1892) follows Langerhans. 
O. Hertwig (‘‘ Die Chetognathen,” Jenaische Zeitschr. 
Bd. xiv. 1880) makes two genera on the basis of fins alone :— 
Sagitta, with five fins; Spadella, with three. 
Grassi (‘Fauna und Flora d. Golfes von Neapel,’ no. 5, 
1883) takes the ground that fins and teeth are not of suffi- 
cient morphological importance, and bases his two genera on 
the following anatomical characteristics :—Sagitta: transverse 
musculature, adhesive and glandular cells present, some 
tactile prominences somewhat buried in the epidermis. The 
lack of these features characterizes the genus Spadella. 
Since the Chetognaths that have these three features are in 
general those that have three fins, it will be seen that while 
this classification of Grassi’s does not affect the constituency 
of the two genera, it interchanges the names, so that a Sagitta 
of Hertwig is a Spadella of Grassi. ‘This reversion of the 
accustomed names gives rise to unfortunate confusion. 
The difficulty with Spadella schizoptera now is that it has 
the fins of one genus with the morphological characteristics 
of the other. According to Langerhans’ or Hertwig’s systems 
it would have to be called a Sagitta, as having five fins, 
in spite of its distinctively Spadel/a characteristics. On the 
strength of a single external resemblance it would thus be 
separated from its nearest allies. Grassi’s system, while 
keeping it in the same genus as its fellows, would reverse the 
usual name of that genus and call it Sagitta. As the dis- 
tinctive features of the new form did not appear to warrant 
establishing a new genus, it seemed best to classify it, at any 
rate provisionally, according to a combination ot Hertwig’s 
and Grassi’s systems—determining its genus according to the 
morphological characteristics of Grassi, so that it might be 
kept with its nearest allies, but retaining for that genus the 
name (Spadella) it would have in the classification of Langer- 
hans or of Hertwig. 
